1. Field of the Invention
This invention relates to firearms, in particular, to a firearm which is capable of firing different-size cartridges.
2. Description of the Prior Art
One known way of providing a firearm which is capable of firing different-size cartridges is shown in U.S. Pat. No. 4,494,332. In the structure disclosed in the patent, there is disclosed a block which has therein a number of bores which are adapted to receive, for example, cartridges which are of the same caliber but of different lengths, each bore containing in a part distal from the user an internally threaded part for receiving screwingly the proximal end of the barrel of the firearm. The barrel is shown as being threaded only on one end, but it is capable of being brought into engagement with the desired one of the bores, in accordance with the size of the cartridge to be fired. With the structure according to U.S. Pat. No. 4,494,332 it is necessary, when changing the size of the cartridge to be fired, not only to remove the barrel from one bore end and insert it into another, but also to rotate the block containing the bores so that a desired and appropriate one is brought into alignment with the apparatus for delivering into a suitably fitting bore the cartridge which is to be fired. There has been a need in the art for a structure which will accomplish the same result with less weight and with less manipulation, when changing from one cartridge size to another.
There exist in the prior art some examples of a rifle barrel having external threading at each end of the barrel. Such barrels can be seen, for example, in German Pat. No. 730,030, issued in 1943, and in Swiss Pat. No. 279,655, published in 1952. These patents lack, however, both the idea of providing different-length enlarged bores in the opposite ends of the barrel and the idea of considering the barrel reversible, i.e., such that either one end or the other thereof may be used as the proximal portion of the rifle barrel, in accordance with the length of the ammunition which is desired to fire.